Abstract
The relationship between covert shift of attention and the oculomotor system has been the subject of numerous studies. A widely held view, known as Premotor Theory, is that covert attention depends upon activation of the oculomotor system. However, recent work has argued that Premotor Theory is only true for covert, exogenous orienting of attention and that covert endogenous orienting is largely independent of the oculomotor system. To address this issue we examined how endogenous and exogenous covert orienting of attention was affected when stimuli were presented at a location outside the range of saccadic eye movements. Results from Experiment 1 showed that exogenous covert orienting was abolished when stimuli were presented beyond the range of saccadic eye movements, but preserved when stimuli were presented within this range. In contrast, in Experiment 2 endogenous covert orienting was preserved when stimuli appeared beyond the saccadic range. Finally, Experiment 3 confirmed the observations of Exp.1 and 2. Our results demonstrate that exogenous, covert orienting is limited to the range of overt saccadic eye movements, whereas covert endogenous orienting is not. These results are consistent with a weak, exogenous-only version of Premotor Theory.
Highlights
Every day we are faced with numerous visual inputs that our visual system needs to filter in order to select the information of interest
Initial fixation positon To ensure that each participant was presented with the placeholder at the accurate eccentricity, it was important that they were correctly positioned at the centre of the screen at the beginning of each trial
Pairwise t-tests showed that the difference in mean Reaction Times (RTs) observed between Valid and Invalid condition was only significant for Below effective oculomotor range (EOMR) condition (Invalid Below 1⁄4 508 msec, SD 1⁄4 153, Valid Below 1⁄4 498 msec, SD 1⁄4 160, t(22) 1⁄4 2.15, Bonferroni corrected p 1⁄4 .025, Invalid Beyond 1⁄4 520 msec, SD 1⁄4 154, Valid Beyond 1⁄4 523 msec, SD 1⁄4 160, t(22) 1⁄4 .66)
Summary
Every day we are faced with numerous visual inputs that our visual system needs to filter in order to select the information of interest This selection can be driven endogenously, by our current goals and desires, or exogenously, in response to salient visual events in the environment (Posner & Cohen, 1980). Under normal circumstances this visual selection is achieved by making a saccadic eye movement that places the object or location of interest on the fovea, greatly enhancing the perception of fine detail. The extent to which covert and overt attention rely on similar cognitive and neural mechanisms is controversial
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